There was a time in the early 1970s when the only banana plugs I could find in the Toronto area were the solderable type (I still have some speaker cables with those plugs attached.)

It certainly isn't necessary, given the significant voltage/amperage of high-level audio signals from a power amplifier. If you were talking about the tiny output from a moving-magnet or moving-coil phono cartridge (a few millivolts--thousandths of a volt), then losses might be significant.

I haven't bothered soldering banana plugs for years. You could take this to ludicrous extremes, the way some tweaks are prone to do--and solder the entire signal path from the amplifier output terminals to the crossover board inside the speaker, but there's no significant--or audible--loss with high-level signals and typical speaker posts and banana plugs so don't worry about it.

I would caution that if your preference is a heavier duty thicker speaker cable, because of the cables extra weight and stiffness, it can actually break off the connection quite easily in which case it would be better to go to a direct wire or spade connection.

These Radio Shack banana plugs let the wire hang down to reduce that problem. I also like that I know that when the wire exits the bottom, they are oriented with the proper polarity, so I don't have to squint to try to determine "red or black". The knurled knob in the back of them tightens down on the wire. They also accept the 12 gauge wire I'm using.